Filter device

ABSTRACT

The invention relates to a filter device comprising a filter housing ( 10 ), a filter inlet ( 12 ), a filter outlet ( 14 ), and a filter element ( 16 ) which divides a filter area ( 18 ) into two partial areas ( 20,22 ). At least one of the partial filter areas is conical in form resulting from the fact that the cross-section of one partial area ( 20 ) is tapered from the filter inlet ( 12 ) to the filter outlet ( 14 ). Said partial areas are separated from each other by said filter element. This results in an optimum residence time distribution inside the filter device at a uniform flow rate, which is particularly useful for highly viscous fluids such as polymer melts or similar.

[0001] The invention relates to a filter device with a filter housing having the characteristics specified in the preamble of claim 1.

[0002] Filter devices of this nature (U.S. Pat. Nos. 4,964,984, 4,169,795, 4,052,315, 4,043,918, and GB 2 075 364) are readily obtainable on the market in a multiplicity of embodiments. The structure itself of the filter elements, which are assigned the function of filtering impurities out of a fluid, is determined by the manufacturer. Filter elements of higher quality have a multilayer meshed structure which may rest at least on one supporting fabric to enable the structure to resist higher pressure or pressure peaks.

[0003] In principle it is desirable to arrive at uniform flow behavior inside the filter space during the filtration process while avoiding dead spaces, the requirements set for the desired behavior increasing as the viscosity of the fluid increases, especially if liquefied polymer materials or polymer solutions are to be filtered.

[0004] U.S. Pat. No. 3,817,377 discloses a generic filter device, in particular one for separation of impurities from hot thermoplastic polymer material. In one embodiment of the conventional filter device shown in FIGS. 4 and 5 a conical filter element subdivides a conical filter space into two conical subspaces, the conicities of the two subspaces extending constantly in opposite directions but to different extents, that is, with different cross-sections relative to one point of reference. The diameter of the filter element is measured from the filter outlet in the direction of the filter inlet more or less constantly and the resulting conicity of the filter element is referred to the longitudinal direction of the filter outlet. The bounding walls following the subspaces as housing elements have a conical orientation comparable to that of the filter element, so that the conventional solution applied for this purpose is complex in structure. Control of flow which is unfavorable from the viewpoint of energy is obtained because of the different cross-sectional patterns referred to one point of comparison, especially in the case of high-viscosity fluids.

[0005] On the basis of this state of the art the object of the invention is to improve conventional filter devices further to the end that filter operation favorable from the viewpoint of energy consumption is allowed. The problem as thus stated is solved by a filter device having the features specified in claim 1 as a whole.

[0006] As a result of the fact that, according to the descriptive portion of claim 1, narrowing of the cross-section of one of the subspaces occurs to the same extent as does widening of the cross-section of the other subspace, that one of the subspaces extending outward toward the exterior and the other subspace inward toward the center of the filter device are each bounded by a cylindrical wall, and that the filter element narrows conically in the direction from the filter outlet to the filter inlet, because of the equally varying cross-sections of the two subspaces an optimal dwell time distribution is achieved, along with uniform rate of flow of fluid of especially high viscosity, such as one in the form of liquefied polymer material or a polymer solution. Another result is that in filtering operation dead spaces inside the filter housing may be prevented and uniform distribution of the mass to be filtered. This results in filtration operation with acceptable energy costs and in cost reduction. In addition, the fluid to be filtered expands from a narrow cross-section toward a wide cross-section and, conversely, from a wide subspace into a subspace with correspondingly narrowed cross-section.

[0007] In order to obtain conical subspaces provision is made such that the filter element itself is conical in form and tapers from the filter outlet in the direction of the filter inlet. Accordingly, as viewed in the fluid or filter direction, the subspace with the cross-section tapering toward the filter outlet is mounted upstream from the filter element, and the other, conversely, the subspace with the widening cross-section, downstream beyond the filter element. Provision is preferably made such that the filter element has a supporting tube and such that the filter material is mounted on the supporting tube so as to be replaceable. The measure first named ensures that the filter element is able to perform its function when subjected to high pressures, while the other measure or clear-cut definition of features makes certain the filter element material, once depleted, can be replaced with new material without making complete replacement of the filter element plus supporting tube necessary. The filter housing is preferably cylindrical in form, at least in the area of the filter element introduced.

[0008] In an especially preferred embodiment of the filter device claimed for the invention the filter inlet and outlet have cross-sections open in the direction of the filter space so that uniform distribution of the fluid to be filtered is also ensured in these locations. The filter housing, filter inlet and outlet, and the filter element with supporting tube and filter material preferably consist of special steel materials.

[0009] The filter device claimed for the invention is described in detail in what follows with reference to an embodiment illustrated in the drawing.

[0010] In the drawing, in outline and not drawn to scale,

[0011]FIG. 1 shows, partly as a side view, partly in longitudinal section, the filter device as a whole;

[0012]FIG. 2 shows the filter, element illustrated in FIG. 1, partly as a side view, partly in longitudinal section;

[0013]FIG. 3 shows, partly as a side view, partly in longitudinal section, an enlargement of the lower connection area of the filter device shown in FIG. 1.

[0014] The filter device, essentially cylindrical as a whole, has a filter housing 10 and filter inlet 12 and filter outlet 14. A filter element 16 as a whole is mounted inside the filter housing 10. This element subdivides a filter space 18 into a first subspace 20 and a second subspace 22. The subspace 20 first named tapers, as is shown in FIG. 1 in particular, from the filter inlet 12 to the filter outlet 14 in free cross-section. The other, second, subspace 22, on the other hand, widens from the filter inlet 12 to the filter outlet 14 in cross-section. The tapering of one subspace 20 in cross-section proceeds to the same extent and steadily as does widening of the other subspace 22 in cross-section. Hence the two subspaces 20, 22 referred to are juxtaposed so as to be conical in form. In addition, the subspaces 20, 22 form closed ringshaped chamber structures inside the filter device.

[0015] The filter element 16, which itself is conical in shape and tapers conically from filter outlet 14 to filter inlet 12, is used to create the conicity in the subspaces 20, 22.

[0016] The filter element 16 has meshed filter material 24 the inner circumference of which rests against a supporting tube 26 with fluid passages. The filter material 24 surrounds the supporting tube 26 on the outer circumference and is applied around the supporting tube 26 as a filter mesh. The filter housing 10, on the other hand, is cylindrical in shape in the area into which the filter element 16 is introduced. As is also to be seen in FIGS. 1 and 3 for the lower area, the filter inlet 12 and the filter outlet 14 have opening cross-sections to the filter space 18 which are free so that a uniform distribution of the rate of movement of the fluid to be filtered, especially fluid in high-viscosity form such as liquefied polymer material or a polymer solution, is ensured. In the last-named case the filter housing 10, the filter inlet 12, and the filter outlet 14, as well as the filter element 16 with supporting tube 26 and filter material 24, are made of special steel material.

[0017] As the illustration in FIG. 2 shows, the filter element 16 may also be constructed without a supporting tube 26 and the filter material 24 in the form of a special steel mesh is introduced so as to be self-supporting between end caps 28 and 30. As viewed in the line of vision of toward the figures, in the area of the upper end cap 28 the free end of the hollow cylindrical filter material 24 is bent inward and so forms a point of application 32 on the upper end cap 28. The end caps 28, 30 are thus rigidly connected to the filter material 24 and may be pulled away with it, to the extent it is present, from the supporting tube 26 and disposed of separately, if the degree of fouling makes this necessary. New, unused filter material 24 with corresponding end caps 28, is then forced onto the supporting tube 26 or is inserted together with it into the filter device as a component.

[0018] As FIG. 1 also shows, the filter element 16 is fixed in place between an upper receptacle element 34 and a lower receptacle element 36. On its free end the upper receptacle element 34 has a conical guide cone which, together with the upper cover element 38 of the filter housing 10, delimits a fluid channel 40, which forms a circulating ring channel and which is configured in its cross-sectional form as illustrated so that a uniform inflow of the high-viscosity into the first subspace 20 results. For this purpose the fluid channel 40 narrows on its free frontal end by way of which it discharges into the first subspace 20, opposite the entry point extending in the same form at the fluid inlet 12. The direction of delivery of the fluid is indicated by an arrow in FIG. 1, as is also the direction of drainage at the filter outlet 14.

[0019] The fluid flowing through the filter device in the direction of the arrow, which is charged with fouling on the filter inlet 12 side, thus passes through the fluid channel 40 into the first conical subspace 20 and fills this subspace so that there is no dead space. In the event of a uniform dwell time in the first subspace 20, the fouled fluid passes evenly and constantly through the filter material 24 and is there suitably filtered clean. The cleaned fluid then passes by way of the free passage points of the supporting tube 26 into the second subspace 22 and by way of the latter and the other fluid channel 42 on the filter outlet 14 from the filter device, now cleaned. As regards the double conicity of the two subspaces 20, 22 mounted so as to extend in opposite directions, it is characterized by uniform rate of flow, so that optimal dwell time distribution over the filter element is ensured.

[0020] Inside the filter device the receptacle element 34 rests on a rod-shaped filter element 44, which preferably is also is made of special steel material. The filter element 44 may also be guided inside the filter device by way of the receptacle element 34 and fixed in position inside this filter element 44. The filter housing 10 has a cylindrical central housing section 46 which is rigidly connected to the upper cover element 38 and the lower cover element 50 by way of the weld joints 48 on the edge. The lower cover element 50 holds the lower receptacle element 36 on the filter housing 10 in place by way of a screw connection 52, thereby immobilizing the filter element 16 inside the filter space 18 as a whole. The upper cover element 38, as viewed in the direction of FIG. 1, narrows in diameter upward and forms a connection point for a swivel nut 54 by way of which a feed connection piece 56 for delivery of liquefied polymer material may be connected. There is provided on the opposite end of the filter device a corresponding swivel nut 58 by way of which a drain connection piece 60 for discharge of the filtered fluid in the form of purified liquefied polymer material is connected to the filter device. A corresponding threaded section (not shown) facilitates the pertinent fastening.

[0021] Loosening of the screw connection 52, which comprises several fastening screws mounted radially over the circumference of the filter device, permits detachment of the lower receptacle element 36 and removal of the filter material 24 with and without supporting tube 26. Filter element replacement can thus be carried out quickly. The filter element 16 and thus the filter material 24, as well as the two subspaces 20, 22 as thus conditioned, exhibit only slight conicity, for example, in the form of inclination relative to the horizontal and/or in the transverse direction of the filter device of the order of magnitude of 1° to 5°. 

1. A filter device with a filter housing (10), a filter inlet (12) and filter outlet (14), and a conical filter element (16) which subdivides a filter space (18) into two subspaces (20, 22) from the filter inlet (12) to the filter outlet (14), one subspace (20) tapering conically in cross-section from the filter inlet (12) to the filter outlet (14) and the other subspace (22) widening conically in cross-section from the filter inlet (12) to the filter outlet (14) and the conicities of the two subspaces (20, 22) proceeding constantly in opposite directions, characterized in that the narrowing of the cross-section of one subspace (20) occurs to the same extent as the widening of the cross-section of the other subspace (22), in that one subspace (20) extending outward to the exterior and the other subspace (22) extending inward to the center of the filter device are each bounded by a cylindrical wall, and in that the filter element (16) narrows conically from the filter outlet (14) toward the filter inlet (12).
 2. The filter device as specified in claim 1, wherein the bounding cylindrical wall for one subspace (20) is in the form of the filter housing (10) and for the other subspace (22) in that of a rod-shaped filter element (44) which extends in the center along the filter device in its interior.
 3. The filter device as specified in claim 1 or 2, wherein the filter element (16) has a supporting tube (26) and wherein the filter material (24) is fastened to the supporting tube (26) so as to be replaceable.
 4. The filter device as specified in one of claims 1 to 3, wherein the filter housing (10) is cylindrical in shape at least in the area of the filter element (16) introduced.
 5. The filter device as specified in one of claims 1 to 4, wherein the filter inlet (12) and filter outlet (14) have free opening cross-sections in the direction of the filter space (18) such that a uniform rate of flow of the fluid to be filtered is ensured.
 6. The filter device as specified in claim 5, wherein the fluid to be filtered is of high viscosity, and in particular is liquefied polymer material or a polymer solution.
 7. The filter device as specified in one of claims 1 to 6, wherein the filter housing (10), the filter inlet (12) and filter outlet (14), and the filter element (16) with supporting tube (26) and filter material (24) consist of special steel material. 